Tuesday, April 11, 2017, 10:50 - Britain's ancient monument Stonehenge is still revealing secrets 4,500 years after the stone circle was first erected in the late Neolithic period.

Many theories have been suggested as to its exact purpose, but modern archaeologists generally agree it was some sort of prehistoric temple aligned to the movements of the sun.

But it seems that these famous standing stones were positioned to enhance their acoustic properties as well.

Researchers from the University of Huddersfield conducted mathematical acoustic analysis of Stonehenge's archaeological plan. When digitally reconstructed, the stones' original placing revealed surprisingly sonorous properties.

"If you build something that is circular, it has circular acoustics. So the acoustic and the sound of the space comes from the shape of its design. So when it was designed in the particular shape it has, in particular the circles, it created visual effects. But it also created acoustic effects," lead researcher Dr Rupert Till told Reuters.

Stonehenge in the southwest English county of Wiltshire remains a magnet for hippies and modern-day druids, though worries about damage means tourists can no longer wander amongst the stones.

In the 19th century, visitors could hire chisels at the site to hack off their own souvenirs from the stone.

"What we see at Stonehenge today is pretty much a ruin. There's a lot of it still here, but perhaps half the stones are missing," said Till.

"Today you can still hear some echoes, so you hear the birds calling or if you clap your hands or if you play a musical instrument, you hear quite a subtle echo. But if you're listening, it is clearly there. You also have a sense of reverberation, a bit like a gigantic bathroom. People say 'well, you hear that anywhere'. But not two-thousand, three-thousand years ago; there weren't any large stone buildings. So this would have been one of the few human-made places where you'd have heard these kind of acoustic effects."

Till was granted permission from custodians English Heritage to experiment among the monoliths of Stonehenge.

"One of the test signals we use in acoustics a lot of the time is a hand clap. It's a simple way to hear what the space sounds like. And when you clap your hands, the sound leaves your hands, goes off, then it hits all the stones in the circle and comes back. And because I'm right in the centre there's a a focus [of these reflections]. So the sound goes out and you hear a slight echo afterwards," Till explained as he clapped his hands with the sound reverberating around.

He also used a variety of replica instruments from the era, including a drum and cow horn, to identify how sound moved around the stones even in their partially ruined state.

Using this data, the Huddersfield research team built a digital model of Stonehenge using computer game software, with the standing stones recreated in all their prehistoric glory.

Till composed an interactive soundscape for the model, with the sound of birds and the wind moving through the stones, as well as a soundtrack of Neolithic 'music'. He added that the stones had acoustic features as good as some concert halls, and are particularly suited to loud rhythmic music.

A 'virtual tour' of Stonehenge called the Soundgate is being released as an app that transports people back to various eras in Stonehenge's history, including when the standing stones were at their zenith, and long before the traffic noise from the nearby A303 road.

Using a smartphone or tablet, and with a pair of headphones, users can move around the digitally reconstructed stone circle while listening to the changing acoustics.

"Over time the monument has developed, and our app shows different phases of that development so you can see what it looked like 5,000 or 4,000 years ago, through a thousand years of development," added Till.

Stonehenge is an enigmatic location often shrouded in mysticism and the occult. However, scientist Till would not be drawn on whether he thought Stonehenge was built to amplify otherworldly sounds or act as some sort of celestial calendar.

"We can never be sure which was most important to people in the past," he said.